The Mycobacterium tuberculosis Rv0132c Gene Product Mtb-FGD2 Can Act as an F420-Dependent Glucose Dehydrogenase.

The role of the cell envelope-associated Rv0132c/FGD2 from Mycobacterium tuberculosis has long been a subject of debate. Importantly, FGD2 is found only in pathogenic mycobacteria, making it a potential drug target. While some suggest it functions as a glucose-6-phosphate dehydrogenase, others propose it acts instead as an F420-dependent hydroxy-mycolic acid dehydrogenase-an activity linked to cell-wall remodeling and inhibition by the anti-tubercular drug pretomanid. Yet, direct evidence for either activity has been lacking. Here, we heterologously express and purify active Mtb-FGD2, and demonstrate that the enzyme binds the F420 cofactor with nanomolar affinity. Crystal structures for both the apo-form and the F420 complex reveal that the Mtb-FGD2 active site architecture is consistent with sugar substrates but notably lacks a phosphate-binding pocket. Biochemical assays confirm that Mtb-FGD2 functions efficiently as an F420-dependent glucose dehydrogenase in vitro. Computational docking combined with molecular dynamics simulations further supports the formation of a catalytically plausible β-D-glucose:F420 ternary complex. When coupled to other F420-dependent enzymes, Mtb-FGD2 readily supports glucose-driven F420.H2-dependent oxidoreductase activity. Our data thus suggest that the Mtb-FGD2 provides reduced F420.H2 in a glucose-dependent manner to support mycobacterial F420.H2-dependent oxidoreductases in the cell envelope.